I've kept track of everything since I've owned my '99. I purchased my 4Runner in '07 from it's second owner. They had it for a year and had no records. I've stumbled across some stuff on line for it but everything else I've done, even marker light bulb changes, get's logged.
I have a small spiral book in the glove box with a short blurb of what was done (oil changes, rotations and even things like install of a bumper, skids, sliders, etc), the date and mileage. Receipts and all paperwork go in a binder in the garage next to a binder that holds an FSM and wiring diagram for it.
Even mods I've done, especially electrical, get a page or two. It might be notes or even a hand drawn wiring diagram but it's all there.
I do the same for my house. I got nothing with my house and after I bought it I had tons of questions with no answers. I've got a house binder with sprinkler pipe diagrams drawn on Google aerials, dates things were taken out, replaced or installed. It helps me because something might go bad while under warranty. It's nice to know when and where I bought it not to mention the receipt. Every once in awhile I'll snap before and after pictures of projects. It's only been 5.5 years of ownership but it's fun to look back on where I started. I hope to knock the socks off the folks I sell it to one day.